1. Technical Field of the Invention
The present invention relates to an apparatus for controlling headlights mounted on a vehicle, and in particular, to the apparatus for controlling the angle of a light axis of light to be radiated from the headlights in consideration of preceding vehicles which run ahead of the vehicle equipped with the apparatus.
2. Description of the Related Art
Recently there have been known techniques to control the light axes of the head lights of a vehicle. One such technique is for preventing a vehicle's driver from being dazzled by light radiated by a vehicle running behind. This technique is disclosed by International Patent Publication No. 2001/070538, for example, in which a distance from a preceding vehicle is detected and, on the basis of the detected distance, the direction (i.e., angle) of light axes of headlights is controlled. Practically, in the foregoing publication, as the distance is shorter, the light-axis direction of the head lights is lowered downward. That is, when the distance is longer, the light-axis direction of the head lights is raised upward.
However, the foregoing publication discloses only a conception, not a practical control way. Hence, relying on this disclosed technique is insufficient for controlling appropriately and smoothly the light-axis direction of the head light. For example, when the light-axis direction is controlled excessively upward, the driver in a preceding vehicle may be dazzled by the upwardly radiated light. In contrast, an excessively downward light-axis direction may cause a dark area between the area lit by the headlights of the vehicle and a preceding vehicle running in front of the vehicle.